Earlier quoted context omitted.
Replace tail by arm in your comment and see what is wrong about it.
Arms are powerful but tails are not.
Crocodiles disagree.
Scientists have traced human tail loss to a short sequence of genetic code
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Re: Scientists have traced human tail loss to a short sequence of genetic code
#22My favorite "Scan Scene" from The Congress (Ari Folman's film based on Stanislaw Lem's novel "The Futurological Congress"), in which Harvey Keitel's character "Al" tells Robin Wright's character "Robin" the twisted tail of "Joey Fairytail"... https://www.youtube.com/watch?v=pPAl5GwvdY8
I love the book!
Re: Scientists have traced human tail loss to a short sequence of genetic code
#23A tail is grabbable. I'd think in primate fighting, a tail would be big negative. It could be grabbed. Can you imagine Chimp fights if they had tails that could be held on to and the owner dragged around.
I don't follow. You can grab leg and drag owner around. How's tail different?
A leg has rigidity due to its endoskeleton, as well as strong muscles with good leverage, which when conditions are right gives it insane strength as it can act as a mechanical lever.
Since a tail does not have a rigid endoskeleton, it can not act well as a lever. It's functionally a rope attached to your butt. Like even if you go full kangaroo mode and make the tail more muscular than the legs, making the tail rigid by flexing really hard, it basically turns into an inefficient leg with enormous mechanical disadvantages.
Re: Scientists have traced human tail loss to a short sequence of genetic code
#24My favorite "Scan Scene" from The Congress (Ari Folman's film based on Stanislaw Lem's novel "The Futurological Congress"), in which Harvey Keitel's character "Al" tells Robin Wright's character "Robin" the twisted tail of "Joey Fairytail"... https://www.youtube.com/watch?v=pPAl5GwvdY8
I love the book!
"The Congress" is to "The Futurological Congress" is to Stanislaw Lem like "Blade Runner" is to "Do Androids Dream of Electric Sheep" is to Philip K Dick.
Both great movies loosely based on both great but very different books by great authors, each with something unique and deep and important to say, that all stand on their own and are worth knowing.
Re: Scientists have traced human tail loss to a short sequence of genetic code
#25A tail is grabbable. I'd think in primate fighting, a tail would be big negative. It could be grabbed. Can you imagine Chimp fights if they had tails that could be held on to and the owner dragged around.
I don't follow. You can grab leg and drag owner around. How's tail different?
Legs have a lot more muscle to allow the owner to resist, along with the downward weight of the body somewhat adding to stability?
Re: Scientists have traced human tail loss to a short sequence of genetic code
#26[flagged]
Re: Scientists have traced human tail loss to a short sequence of genetic code
#27A tail is grabbable. I'd think in primate fighting, a tail would be big negative. It could be grabbed. Can you imagine Chimp fights if they had tails that could be held on to and the owner dragged around.
Hair is much worse in that regard, as the tail would be positioned too low to practically grab (it would asking for a knee to the face or punches to the back of the head or spine if you tried). I think the driver is more likely to be bipedality. A tail doesn't provide a lot of benefit for balance or rearside whisker utility when moving on two legs, and would interfere with sitting and lying postures. I think humans are probably too large for practical prehensile tails too.
Re: Scientists have traced human tail loss to a short sequence of genetic code
#28Monkeys have tails to swing and walk in trees.
Re: Scientists have traced human tail loss to a short sequence of genetic code
#29It takes metabolic resources to grow a tail. If the benefit was less than the cost, mutations that prevented the tail from growing were selected for.
Re: Scientists have traced human tail loss to a short sequence of genetic code
#30They buried the lede: Even if the driving mutation identified in the study could be undone, “it still wouldn’t bring back the tail.” Oh well.
So I’m guessing this is less like, “we found the flag that toggles tail production” and more “we found a chunk of code that belongs to tail production”? The first bit of the article sure makes it sound like this DNA is what does it all.
The scientists believed that the extra AluY element was functionally working to block out a part the TBXT gene (exon6). In their mouse model, they first directly snipped out exon6, and found that mice that were heterogeneous wildtype TBXT and exon6 removed TBXT developed a full spectrum of tail phenotypes from no tail to full length tail. At this point, the statement is "These results provide further evidence that the presence of TBXTΔexon6 is sufficient to induce tail loss".
They then tried to "more realistically" replicate the scenario. Instead of just snipping out exon6, they tried inserting in various elements into the mouse TBXT gene to emulate their model of how AluY is cutting out exon6. They attempted a few different methods which resulted in different models that would end up with different relative amounts of TBXT missing exon6 being produced. I'm having a hard time tracking all their conditions and lines at this point, but they seem to claim here that higher amounts of exon6 drop out correspond to shorter tails.
They also found that they could not get any viable mice with exon6 snipped from both copies of TBXT.
TBXT itself is a transcription factor, meaning that it controls the expression of other genes. There's probably a set of genes elsewhere that together make up the "tail-making machinery" that TBXT heavily interacts with. In this sense, TBXT 'might' be the most important single point lever, but at the same time not be fully in control of the underlying machine.
What does seem persuasive is that idea that this mutation kicked off some rate of tail lose in our ancestors, which then lead to some sort of selection advantage. The advantage was then made more durable by accumulating additional mutations to lock in the phenotype. In addition, once the "tail making machinery" is inactive, we have no idea how those genes might have been repurposed. I think it's in this sense that the scientists say that we probably can't bring tails back just by "fixing TBXT".